SATURDAY, July 30, 2005 (HealthDayNews) -- With West Nile virus now present in all 48 contiguous states, avoiding infection has become a seasonal concern for nearly all Americans.
The virus, which made its U.S. debut in New York City in 1999, is spread by mosquitoes that pick it up when feeding on infected birds and animals. Humans, in turn, contract the virus when bitten by infected mosquitoes. High season is primarily late summer or early fall.
A relatively small proportion of people infected -- about one in 200 -- will become seriously ill with West Nile encephalitis, the potentially fatal swelling of the brain that is the virus's most serious effect. Another 20 in 200 will experience less severe flu-like symptoms, including fever, headache and fatigue.
Individuals over the age of 50 and those with weakened immune systems are the most vulnerable to serious illnesses. In the first U.S. outbreak in 1999, 55 people in New York City were hospitalized and seven died, most of them elderly.
The best thing Americans can do is avoid getting bitten. Here are some prevention tips:
More information
For more on West Nile virus, head to the Centers for Disease Control and Prevention.